1. Technical Field
The present invention is in the field of RF ranging and locating. It describes a method to determine the time of arrival of a ranging signal.
2. Discussion of Related Art
Systems for estimating the location of a device (locating systems) or the distance between two devices (ranging systems) based on the transmission and reception of electromagnetic waves are commonly used.
Many of such locating systems rely on the estimation of the time difference of arrival (TDOA) of a signal at different receivers or of different signals at one receiver. Many of such ranging systems rely on the estimation of the time of flight (TOF) of the signal between a transmitter and a receiver. The estimation of TDOA as well as the estimation of TOF rely on the estimation of the absolute or relative time of arrival (TOA) of a signal.
A common problem in receivers, which perform such timing estimation is that not only the direct wave is received but also reflected waves.
For a TOA measurement, only the direct wave is relevant, the other waves are interference. As a result of the channel impulse response, an overlap of the direct wave and the reflected waves is observed at the receiving antenna. The TOA measurement then gets an error.
By doing repetitive measurements, one can average out certain errors. However, because the propagation environment may change very slowly or can even be quasi-static, this does not necessarily work in order to eliminate errors caused by multipath reflections.